The present invention relates to a polishing machine, more precisely, it relates to a polishing machine, which has a polishing plate for polishing works; a center roller being coaxial to the polishing plate, a plurality of guide rollers arranged around the center roller for rotatably holding the works with the center roller; and an arm shaft having a work head for holding and releasing the work so as to transfer the work.
Conventionally, a polishing machine, for example, for polishing silicon wafers (works) is known. One conventional polishing machine is disclosed in the Japanese Patent Kokai Gazette No. 4-53674. The disclosed polishing machine has a circular polishing plate, which is capable of revolving so as to polish silicon wafers. A center roller is rotatably provided at a center of the polishing plate. A plurality of guide rollers are rotatably arranged around the center roller with regular intervals. The circular silicon wafers are respectively adhered on one face of each carrying plate, and each carrying plate is rotatably held between an outer circumferential face of each guide roller and that of the center roller. An arm shaft is provided between two adjoined polishing machines, and moved in the longitudinal direction by an air cylinder unit. A work head, which is capable of holding and releasing the carrying plate with the wafer, is provided at a front end of the arm shaft. The work head is capable of moving between a discharge position on the polishing plate of one of the polishing machines and a supplying position on a polishing plate of the other polishing machine.
However, the conventional polishing machine has a following disadvantage.
When the carrying plate with the wafer is discharged from the discharge position of the one polishing machine, the carrying plate, which was held between the center roller and the guide roller, must be moved away from the center roller and the guide roller. If the carrying plate, which is held by the center roller and the guide roller, is lifted by the work head, the wafer may be caught and damaged by the center roller and the guide roller. To avoid the damage, the conventional polishing machine has an air cylinder unit, which moves the arm shaft in the longitudinal direction so as to move the carrying plate away from the center roller and the guide roller before lifting the carrying plate. After the arm shaft is moved in the longitudinal direction by the air cylinder unit, the arm shaft is turned to transfer the carrying plate to the supplying position of the adjacent polishing machine.
To move the carrying plate away from the center roller and the guide roller and to turn the arm shaft with the work head so as to transfer the carrying plate to the adjacent polishing machine, the arm shaft is moved in the longitudinal direction, so that a stroke of the movement of the arm shaft should be relatively longer. With the longer stroke of the arm shaft, in some cases based on positions of the arm shaft, the arm shaft interferes with other carrying plates or other members. Therefore, the position or the design of the arm shaft is limited.